Field of the Invention
This invention relates generally to a system and method for providing lateral steering control assist for lane centering, lane keeping, lane changing, collision imminent steering, etc. in an autonomously driven or semi-autonomously driven vehicle and, more particularly, to a system and method for providing lateral steering control assist for lane centering, lane changing, lane keeping, lane following, a collision imminent steering, etc. in an autonomously driven or semi-autonomously driven vehicle, where the system and method provide a preview of upcoming curved, banked and/or sloped roadways.
Discussion of the Related Art
The operation of modern vehicles is becoming more autonomous, i.e., the vehicles are able to provide driving control with less driver intervention. Cruise control systems have been on vehicles for a number of years where the vehicle operator can set a particular speed of the vehicle, and the vehicle will maintain that speed without the driver operating the throttle. Adaptive cruise control systems have been recently developed in the art where not only does the system maintain the set speed, but also will automatically slow the vehicle down in the event that a slower moving preceding vehicle is detected using various sensors, such as radar and cameras. Certain modern vehicles also provide autonomous parking where the vehicle will automatically provide the steering control for parking the vehicle. Some vehicle systems providing automatic braking without driver intervention to avoid rear-end collisions. As vehicle systems improve, they will become more autonomous with the goal being a completely autonomously driven vehicle. For example, future vehicles probably will employ autonomous systems for lane changing, passing, turns away from traffic, turns into traffic, etc.
Collision avoidance systems are known in the art for providing automatic braking and/or steering of a subject vehicle to avoid a slower or stopped object in front of the subject vehicle in the event that the vehicle driver does not take evasive action. Known collision avoidance systems provide warnings to the vehicle driver and depending on whether the driver takes evasive action, may provide automatic braking and/or automatic steering. If the system determines that automatic steering is necessary to avoid a collision, the system must calculate a safe steering path for the subject vehicle to provide the steering control. Some of those systems are able to detect lane markings so as to calculate the steering path of the subject vehicle to make a lane change for collision avoidance purposes. Those collision avoidance systems also provide steering commands that cause the subject vehicle to follow the calculated steering path to provide the vehicle steering.
The object detection sensors for these types of systems may use any of a number of technologies, such as short range radar, long range radar, cameras with image processing, laser or lidar, ultrasound, etc. The object detection sensors detect vehicles and other objects in the path of a subject vehicle, and the application software uses the object detection information to provide warnings or take actions as appropriate. The warning can be a visual indication on the vehicles instrument panel or in a head-up display (HUD), and/or can be an audio warning or other haptic feedback device, such as seat shaking. In many vehicles, the object detection sensors are integrated directly into the front bumper or other fascia of the vehicle.
Various systems are known in the art for autonomously driven or semi-autonomously driven vehicles that employ suitable controllers, sensors, steering actuators, etc. that provide automatic vehicle steering for one or more of lane centering, lane keeping, lane changing, collision avoidance, etc. For example, U.S. Pat. No. 8,903,607 issued Dec. 2, 2014 to Lee et al., titled, Lane Tracking System With Active Rear-Steer, discloses a lane tracking system that determines a desired course of a vehicle along a roadway, estimates a trajectory of the vehicle based on sensed vehicle motion, computes an error between the determined desired course and the estimated trajectory, and provides a front steering torque command to a front steering controller and a rear steering torque command to a rear steering controller to minimize the error.
U.S. Pat. No. 8,849,515 issued Sep. 30, 2014 to Moshchuk et al., titled, Steering Assist in Driver initiated Collision Avoidance Maneuver, discloses a collision avoidance system that identifies a collision threat, calculates an optimal collision avoidance path, and provides a steering assist torque for steering the vehicle along the path.
U.S. Pat. No. 8,170,739 issued May 1, 2012 to Lee, titled, Path Generation Algorithm for Automated Lane Centering and Lane Changing Control System, discloses a system for providing path generation for automated lane centering and/or lane keeping purposes. The system detects lane markings on the roadway and generates a desired vehicle path that maintains the vehicle in the lane.
U.S. Patent Application Publication No. 2015/0158528 to Moshchuck et al., titled, Collision Avoidance Control Integrated with EPS Controller, discloses a model predictive control (MPC) that employs a six-dimensional vehicle motion model including a combination of a one-track linear bicycle model and a one-degree of freedom steering column model to model the vehicle steering to provide a torque overlay command for steering assist.
The known systems generally referred to above for providing lane centering, lane keeping, lane following, collision imminent steering, steering angle assist, etc. for autonomously and semi-autonomously driven vehicles typically use fused sensor data available at any particular point in time. However, upcoming road changes, such as curves, banks, slopes, etc., in the roadway are typically not fully processed in the control architecture for these systems. For example, segments of a roadway that have sudden horizontal curvature changes are the most challenging situation for autonomously driven vehicle control. The performance requirements for active safety features in these types of system impose a strict limit on the lateral deviation on a curved roadway.